[mapserver-users] MapCache: Disabling WMS requests for fully-seeded caches?

[John Taranu]

Note that setting the default format to PNG doesn't cause a segmentation
fault:


   <default_format>PNG</default_format>
   <errors>empty_img</errors>

However, in this case mapcache still returns a HTTP 404 instead of a blank
image.  



-----Original Message-----
From: Travis Kirstine [mailto:traviskirstine at gmail.com] 
Sent: Tuesday, November 29, 2011 3:21 PM
To: thomas bonfort
Cc: John Taranu; mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] MapCache: Disabling WMS requests for
fully-seeded caches?

Thomas,

Here is the backtrace:

(gdb) run -X
Starting program: /usr/sbin/httpd -X
warning: no loadable sections found in added symbol-file system-supplied DSO
at 0x2aaaaad1b000 [Thread debugging using libthread_db enabled]

Program received signal SIGSEGV, Segmentation fault.
0x00002aaaaca4e32b in strstr () from /lib64/libc.so.6
(gdb) bt
#0  0x00002aaaaca4e32b in strstr () from /lib64/libc.so.6
#1  0x00002aaab539737d in mapcache_image_create_empty () from
/usr/lib64/httpd/modules/mod_mapcache.so
#2  0x00002aaab53971fe in mapcache_configuration_parse_xml () from
/usr/lib64/httpd/modules/mod_mapcache.so
#3  0x00002aaab53a047a in mapcache_configuration_parse () from
/usr/lib64/httpd/modules/mod_mapcache.so
#4  0x00002aaab53879e6 in mapcache_add_alias (cmd=0x7fffffffe760, cfg=<value
optimized out>, alias=0x2aaaaae0f850 "/mapcache",
    configfile=0x2aaaaae0f860 "/var/www/html/mapcache/mapcache.xml")
at mod_mapcache.c:502
#5  0x00002aaaaaad5c4b in ?? ()
#6  0x00002aaaaaad60d0 in ap_walk_config ()
#7  0x00002aaaaaad6232 in ap_process_config_tree ()
#8  0x00002aaaaaac1c51 in main ()
(gdb)

#################################################################

MapCache snippet:

 <default_format>mixed</default_format>

 <errors>empty_img</errors>

Regards




On 29 November 2011 11:56, thomas bonfort <thomas.bonfort at gmail.com> wrote:
> I've just tried report_img locally without issues, any chance you can 
> provide a backtrace ?
>
> On Tue, Nov 29, 2011 at 17:32, John Taranu 
> <jtaranu at firstbasesolutions.com> wrote:
>> Hi Thomas,
>>
>> Thanks for the suggestion.  Commenting out the source block disables the
WMS requests.
>>
>> However, the error reporting seems to be broken.  Setting
<errors>empty_img</errors> crashes Apache with a segmentation fault
(mod_mapcache SVN revision 12828).  Setting <errors>report</errors> throws
HTTP 404 responses, which is a more reasonable result.
>>
>> John
>>
>>
>>
>> -----Original Message-----
>> From: thomas bonfort [mailto:thomas.bonfort at gmail.com]
>> Sent: Tuesday, November 29, 2011 10:33 AM
>> To: John Taranu
>> Cc: mapserver-users at lists.osgeo.org
>> Subject: Re: [mapserver-users] MapCache: Disabling WMS requests for
fully-seeded caches?
>>
>> You can do this by commenting out the <source> block from the tileset
once the wanted tiles have been created. You'll probably also want set error
reporting to return blank images from that stage onwards.
>>
>> --
>> thomas
>>
>> On Tue, Nov 29, 2011 at 00:09, John Taranu
<jtaranu at firstbasesolutions.com> wrote:
>>> We have a fully seeded cache that was fully seeded to a polygon outline.
>>> The intent is to serve the tileset through a variety of services 
>>> (WMS,
>>> TMS) using mod-mapcache.
>>>
>>>
>>>
>>> Tiles that are outside the polygon outline but still within the 
>>> polygon bounding box should be blank tiles.  However, a request for 
>>> one of these tiles results in a call to that tileset’s WMS source.
>>> This creates considerable overhead by starting up MapServer and 
>>> writing the resulting tile to the cache.  Is there any way to 
>>> disable the WMS calls for these blank tiles, and instead 
>>> short-circuit the request to return a blank?  That is, once a 
>>> tileset has been fully seeded, is it possible to disable any further 
>>> calls to the WMS, so that requests for tiles that are not in the cache
return a blank?
>>>
>>>
>>> _______________________________________________
>>> mapserver-users mailing list
>>> mapserver-users at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>>
>>
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